Were a young naturalist asked to exemplify what man has learned from the lower animals, he could scarcely adduce a more striking instance than that of a submarine shelly worker teaching him how to execute some of his noblest works. This we have learned from the life and labours of the _Pholas_, of which it has been emphatically said:--"Numerous accounts have been published during the last fourteen years in every civilized country and language of the boring process of the _Pholas_; and machines formed on the model of its mechanism have for years been tunnelling Mont Cenis." In the Eastern Zoological Gallery of the British Museum, cases 35 and 36, as well as in the Museum of Economic Geology in Piccadilly, may be seen specimens of the above very curious order of _Conchifers_, most of the members of which are distinguished by their habits of boring or digging, a process in which they are assisted by the peculiar formation of the foot, from which they derive their name. Of these ten families one of the most characteristic is that of the Razor-shells, which, when the valves are shut, are of a long, flattened, cylindrical shape, and open at both ends. Projecting its strong pointed foot at one of these ends, the _solen_ can work itself down into the sand with great rapidity, while at the upper end its respiratory tubes are shot out to bring the water to its gills. Of the _Pholadæ_, the shells of which are sometimes called multivalve, because, in addition to the two chief portions, they have a number of smaller accessory pieces, some bore in hard mud, others in wood, and others in rocks. They fix themselves firmly by the powerful foot, and then make the shell revolve; the sharp edges of this commence the perforation, which is afterwards enlarged by the rasp-like action of the rough exterior; and though the shell must be constantly worn down, yet it is replaced by a new formation from the animal, so as never to be unfit for its purpose. The typical bivalve of this family is the _Pholas_, which bores into limestone-rock and other hard material, and commits ravages on the piers, breakwaters, &c., that it selects for a home. In the same family as the above Dr. Gray ranks the _Teredo_,[27] or wood-boring mollusc, whose ravages on ships, piles, wooden piers, &c., at sea resemble those of the white ant on furniture, joints of houses, &c., on shore. Perforating the timber by exactly the same process as that by which the Pholas perforates the stones, the Teredo advances continually, eating out a contorted tube or gallery, which it lines behind it with calcareous matter, and through which it continues to breathe the water.